Everyone loves a lively aquarium. People tend to focus their attention on fish who inhabit the top and middle levels of the tank, though. However, there are plenty of bottom-dwelling fish with big personalities and lots of energy who deserve your appreciation, too.
Bronze Corydoras are one such type of freshwater fish.
Background
Members of the Callichthyidae taxonomic family, these fish are part of the so-called “armored catfish” group. They’re known by various other names, including Green Corydoras, Cories, Cory Cats, Bronze Catfish, and Wavy Catfish.
Theodore Gill introduced them to the Western world in 1858, when he described them as Hoplosoma aeneum. The species has since gone through several taxonomic changes to arrive at Corydoras aeneus. The current Latin name derives from the Ancient Greek terms for helmet (kory) and skin (doras) and the Latin word for bronze (aeneus).
Cories as a group are notoriously long-lived fish. C. aeneus, in particular, have been recorded living as long as 27 years, and many aquarists report that 10-20 years is a standard lifespan for these little guys.
Physical Characteristics
You might be wondering why these fish have such a tough (pun intended) nickname as “armored catfish.” That’s because of the two rows of overlapping bony plates (also known as “scutes”) that they sport on each side of their body. These replace the scales present on most fish bodies.
Their bodies are typically catfish-shaped, with a flattened ventral (underside) surface and an arched dorsal (upper) surface. They possess a second defense mechanism in their fins. Each fin has a leading spine, which can be locked into place to prevent predators from swallowing or harming them. Even better (depending on whether you’re the predator or prey), that spine ends in a sharp point and contains a mild poison that further dissuades anyone trying to make a meal out of them.
Bronze and Green Corydoras are two natural morphological variations of the same fish. The bodies of both varieties exhibit an iridescent sheen overlaid on a bronze-to-greenish color base. In addition, aquarists have selectively bred other colors, such as albino and black. Be aware that some unscrupulous fish vendors have been known to inject their Cories with dye to enhance or alter their coloration. As you can imagine, this leads to health problems for the fish and a headache for you.
As part of the same family as common catfish, they also sport two barbels on the upper part of their mouths. These whisker-like sensory organs serve two functions. For one, they help the fish navigate their world, just like regular whiskers do for cats. Secondly, they contain taste buds, so that your Cories know what to eat and what to avoid.
Since what’s on the inside also counts, we can’t forget to mention their labyrinth organ. Despite being avowed bottom dwellers, all Corydoras possess a special additional respiratory organ that allows them to take in air from the surface.
The labyrinth organ is a maze of small compartments covered in thin membranes of folded tissue and blood vessels that absorb oxygen from the inhaled air. Interestingly, this isn’t just a special ability; it’s also a requirement. Cories must use both their gills and their labyrinth organ to breathe, or they’ll die. This explains while you’ll see your Cories occasionally shooting up to the surface of the tank and then back down to their familiar territory; they’re gulping air.
Personality
While sporting layers of armored bone plates might make Cories sound intimidating, they’re actually quite peaceful. They have no known history of harassing other fish; they seem to believe in live and let live.
In fact, they can be quite shy if they’re not kept in the right conditions. In order to bring out their best personality, you need to provide them with lots of hiding places. Ironically, giving them more places to hide seems to increase their confidence about being out in the open.
Additionally, being a schooling fish, it’s imperative that you keep them in a group of at least five individuals. Many people purchase a single Cory or perhaps a pair, planning to use them as tank cleaners. When you consider, though, that they’re typically found in schools of 20-30 fish in their native habitats, you can imagine how lonely that can be. And, if you’re mainly interested in having bottom feeders as a cleaning method, imagine how much more effective five Cories will be, compared to one!
Having more Bronze Corydoras also means more entertainment. They love to hang out as a group and dart around playfully. They also spend lots of time combing the bottom of the tank, searching for food. Once they tire of that, they’ll often rest together, even laying their heads on top of each other’s bodies.
How cute is that?
Don’t worry, though. Your Bronze Corydoras will pay attention to you, too. They’ve been caught “winking” at observers, on occasion. While you might be inclined to think of this as a personal communication to you, it’s actually a way to move oxygen from their mouth to their gut for processing. You’ll notice that this winking only occurs after your Cory has returned from a trip to the surface for air.
Tank Mates
As adorable as Bronze Corydoras are, most people don’t consider them appropriate to be the sole inhabitants of a tank. This begs the question of who to house them with.
The answer is: pretty much any other docile freshwater fish.
These guys play well with everyone. Tetras, Swordtails, Otocinclus Catfish, Guppies, Mollies, Gouramis, and Loaches are just a few of the many potential tankmates. Of course, if you choose other bottom-dwelling fish, make sure that you have enough space for everyone to play nicely together.
Despite being a peaceful species, Bronze Corydoras – like most other creatures – will become aggressive and territorial if there is not enough space or food in its environment.
Natural Habitat
Bronze Corydoras are a South American fish. They’re found in the wild along the eastern side of the Andes mountains. Their range extends from the Caribbean islands of Trinidad and Tobago to the north, all the way down to the Rio de La Plata Basin of the Argentina-Uruguay border region in the south.
They are widely distributed along slow-moving waterways through this range, although they can be found in fast-moving waters, as well. They prefer shallow, muddy environments with lots of plant and animal life that they can dig around in to find food. In such cases, their labyrinth organ becomes particularly useful as a means of deriving additional oxygen that these low-oxygen environments don’t provide.
Aquarium Set-up
Cories prefer a long and shallow tank. This gives them lots of room to frolic along the bottom and reduces the distance they have to swim in order to reach the surface for their breaths of fresh air. Their substrate must be soft to avoid damaging their delicate barbels and to allow them to easily dig around, as they so love to do. Smooth-edged gravel or sand works well.
As mentioned above, the more hiding places they have, the merrier. You’ll want to decorate your tank with a variety of items, such as driftwood, various stones, decorative pieces like castles, and plants. It’s best to avoid air-powered toys that open and close. These can present a safety hazard.
Speaking of plants, Cories love them. Try to incorporate both potted and floating plants. Remember that all Cories are diggers, though, so your potted plants should be in planters instead of the substrate. Even then, you may have to do some repotting on occasion, depending on how devious your fish are.
Floating plants will help regulate the amount of light that enters the tank. This is ideal because Cories also prefer low light environments that replicate their muddy native habitats.
Water Conditions
Corydoras are relatively adaptable fish that can survive in a broader range of water conditions than some other species. That being said, they too have their preferences.
As tropical fish, they prefer warm water, between 72 and 82 degrees Fahrenheit. Their natural habitats are fairly acidic, thanks to the high levels of decaying plant matter present. Wild-caught individuals will therefore prefer acidic water between 5.5 and 7.0 pH. Many captive-bred Cories, though, have been bred to thrive in more neutral water and tolerate a pH between 7.0 and 7.8 best.
Similarly, wild-caught Bronze Corydoras need soft water, whereas captively-bred ones can also tolerate medium to hard. Make sure you know which type you’re purchasing to provide the best conditions for your fish.
Regardless of the parameters that you maintain, frequent water changes are essential. Cories are highly sensitive to ammonia and nitrite buildup. You should aim for a 25% water change weekly, along with frequent testing, to ensure adherence to the necessary parameters.
Feeding Habits
Bronze Corydoras are omnivores, although they have a marked preference for meat meals. Live worms are a particular treat for them, which they will gleefully wrestle out of the gravel or sand and devour.
In general, though, they will happily accept most pellet or flake food. The issue is getting it to them. Since most people keep their Cories in a tank with other species of fish, those other fish tend to gobble up the food before it reaches the bottom feeders. This can even be the case when you use sinking food.
One solution for this problem is to feed your Cories after the tank lights have gone out. This increases the chances that the competing fish will think its bedtime and become less aware of what might be dropped into the tank for your bottom feeders. Plus, Cories often hide during the day and become more active in the evening, increasing the chances that they’ll still be interested in feeding after the lights go out.
Breeding Behavior
Most aquarium hobbyists agree that Bronze Corydoras are easy to breed.
In their natural habitat, the start of the rainy season signals Cories that the time has come. The rains change the water chemistry, which is what you also want to do if you plan to breed your Bronze Corydoras. Ideally, you will be able to set up a dedicated breeding tank to give your fish the privacy and conditions that they need for spawning success. If you can’t do that, a large water change can also signal that the time is right.
Regardless of which method you choose, you’ll enjoy watching your Cories in action. Things start off typically, with a male chasing a female around the tank. He’ll take any opportunity he can to rub his body and barbels against his chosen lady. Once the female consents to him as a partner, she chooses a spawning location (or several) and cleans it to her satisfaction.
Once that happens, things switch up, and the female begins chasing the male. The pair eventually form a “T” embrace, with the male on top and the female underneath. This positioning triggers the release of both eggs and sperm, which the female will grasp in her pelvic fins.
Once fertilized, the female deposits the eggs on her chosen site. Female Bronze Corydoras typically produce 10-20 eggs at a time but can continue this cycle until they have produced a total of more than 200 eggs. And each clutch of eggs can technically be fertilized by a different male. If that sounds like a lot of work, it is. Breeders report that their Cories can often be found resting at the bottom of the tank, breathing heavily, after the spawning frenzy has abated.
Eggs hatch in 3-4 days and grow quickly. After a month, they’ll be about a half-inch in length. Once they reach one inch in size, you can consider introducing them to the regular aquarium. Just make sure that other community tank members won’t think of them as food.
Size Variations
Bronze Corydoras don’t have much variation in size. They typically max out at 2.5 inches as adults. The genus Corydoras as a whole, though, ranges in size from one to four inches in length.
Fact Sheet
Common Name: Bronze Corydoras
Latin Name: Corydoras aeneus
Size: 2.5 inches
Place of Origin: South America
Temperament: docile
Water Level: bottom-dwellers
Tropical / Coldwater: tropical
Preferred PH: acidic to neutral
Soft / Hard Water: prefer soft but will tolerate medium to hard
